Method of manufacturing resin article having plating layer

ABSTRACT

There is provided with a method of manufacturing a resin article having a plating layer. A surface of a polycarbonate member  110  is irradiated with ultraviolet rays, and thereby the surface is modified. A plating layer  130  is formed on the modified surface by electroless plating. Neither a strong acid treatment nor a strong alkali treatment is performed between the modification and the forming.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a resin article having a plating layer.

2. Description of the Related Art

Polycarbonate members have a high transparency and a high mechanical strength. For this reason, a resin article having a plating layer in which the plating layer is provided on a polycarbonate member can be used as, for example, a transparent wiring board, a code wheel for a rotary encoder, or the like.

An electroless plating method is known as a method for providing a plating layer on a resin article. It is generally known that the surface of a resin article needs to be roughened when electroless plating is performed on the resin article. For example, “The Present and Future Trends in Electroless Copper Plating”, Satoru Shimizu, the Journal of the Surface Finishing Society of Japan, vol. 58, No. 2, pp. 81, 2007 discloses a method for performing electroless plating after the surface of a resin article is roughened by using chromic acid. Japanese Patent Laid-Open No. 2008-094923 also discloses a method for performing electroless plating after a cycloolefin polymer member is modified by irradiating the cycloolefin polymer member with ultraviolet rays so as to have a surface roughness of 5 μm or less.

Furthermore, Japanese Patent Laid-Open No. 8-253869 discloses that a relatively smooth surface of a polycarbonate member is modified by irradiating the polycarbonate member with ultraviolet rays, pre-etching the polycarbonate member by using dimethylformamide, and etching the polycarbonate member by using sulfuric acid. The publication also discloses that as a result of performing electroless plating on the thus modified polycarbonate member, a plating layer was deposited. On the other hand, the publication discloses that unlike polycarbonate/ABS alloy resin, a plating layer was not deposited if the order of performing irradiation with ultraviolet rays, pre-etching and etching was changed, which suggests that it is not easy to perform electroless plating on a polycarbonate member.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, there is provided with a method of manufacturing a resin article having a plating layer, including: modifying a surface of a polycarbonate member by irradiating the surface with ultraviolet rays; and forming a plating layer on the modified surface by electroless plating, wherein neither a strong acid treatment nor a strong alkali treatment is performed between the modification and the forming.

According to another embodiment of the present invention, there is provided with a method of manufacturing a resin article having a plating layer, including: modifying a surface of a polycarbonate member by irradiating the surface with ultraviolet rays; and forming a plating layer on the modified surface by electroless plating, wherein an energy density at a primary wavelength of the ultraviolet rays applied to the surface in the modification is 5.0 mW/cm² or less, and an irradiation time is 5 minutes or more.

According to still another embodiment of the present invention, there is provided with a method of manufacturing a resin article having a plating layer, including: modifying a surface of a polycarbonate member by irradiating the surface with ultraviolet rays; and forming a plating layer on the modified surface by electroless plating, wherein the modification is performed such that in the modified surface, an existence ratio of carbon-oxygen double bonds is larger than an existence ratio of carbon-oxygen single bonds.

Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating processing according to one embodiment.

FIG. 1B is a diagram illustrating processing according to one embodiment.

FIG. 2 is a flowchart of processing according to one embodiment.

FIG. 3 is a diagram showing an area irradiated with ultraviolet rays according to Example 1.

FIG. 4 is a diagram showing the reflectance of plating layers formed in Example 1 and Comparative Example 2.

DESCRIPTION OF THE EMBODIMENTS

In order to keep the transparency of a polycarbonate member, it is desirable that the polycarbonate member has a small surface roughness. Accordingly, the present inventors conducted studies to modify a smooth surface of a polycarbonate member by using a mild roughening method, and found that a plating layer is not always deposited sufficiently. For example, a plating layer was not deposited sufficiently when a smooth surface of a polycarbonate member was modified by irradiating the polycarbonate member with ultraviolet rays.

According to one embodiment of the present invention, it is possible to easily produce a polycarbonate member having a plating layer formed thereon.

The present inventors conducted various studies and found that a plating layer is less likely to be deposited when an additional modification treatment is performed on a polycarbonate member that has been modified by ultraviolet rays. Based on this finding, the present inventors have accomplished the present invention. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It is to be noted, however, that the scope of the present invention is not limited to the embodiments described below.

Embodiment 1

A method of manufacturing a resin article having a plating layer according to Embodiment 1 includes a modification step and a plating step. Hereinafter, these steps will be described in detail with reference to FIGS. 1A, 1B and 2.

Modification Step

In the modification step (S210), a surface of a polycarbonate member is irradiated with ultraviolet rays. Through this step, the surface of the polycarbonate member is modified. To be specific, in this step, the polycarbonate member is modified such that a plating layer is deposited at a position irradiated with ultraviolet rays in the plating step (S220), which will be described below. FIG. 1A shows that a modified portion 120 is formed in an area of a polycarbonate member 110 irradiated with ultraviolet rays.

Polycarbonate refers to a polymer in which monomers are bonded via a carbonate group. Generally, polycarbonates manufactured from bisphenol A and phosgene or diphenyl carbonate are used. In one embodiment, the polycarbonate member includes a polycarbonate alone, but in another embodiment, the polycarbonate member may consist substantially of a polycarbonate. To be specific, the weight ratio of polycarbonate included in the polycarbonate member is, according to one embodiment, 80% or more, according to another embodiment, 90% or more, and according to still another embodiment, 95% or more.

There is no particular limitation on the shape of the polycarbonate member 110, and the polycarbonate member 110 may have any three-dimensional shape. For example, the polycarbonate member 110 may be in the form of a film or a plate. The thickness of the polycarbonate member 110 is not particularly limited.

From the viewpoint of ensuring the transparency of the polycarbonate member, according to one embodiment, the polycarbonate member 110 has a smooth surface. For example, a part or all of the surface of the polycarbonate member 110 before being irradiated with ultraviolet rays in the modification step has a surface roughness of, according to one embodiment, 1.0 μm or less, according to another embodiment, 100 nm or less, according to still another embodiment, 10 nm or less, and according to yet another embodiment, 2 nm or less. In this specification, the surface roughness refers to the arithmetic average roughness Ra defined by JIS B0601: 2013. The surface roughness Ra can be calculated by performing measurement using an atomic force microscope (AFM) and then performing cross-section analysis.

Also, a part or all of the surface of the polycarbonate member 110 before being irradiated with ultraviolet rays in the modification step has a maximum height roughness Rz of, according to one embodiment, 1.0 μm or less, according to another embodiment, 100 nm or less, and according to still another embodiment, 10 nm or less. The maximum height roughness Rz is defined by JIS B0601: 2013. The maximum height roughness Rz can also be calculated by performing measurement using an atomic force microscope (AFM) and then performing cross-section analysis.

As will be described later, irradiation with ultraviolet rays may be applied to a portion of the surface of the polycarbonate member 110. In this case, in the plating step (S220), plating can be performed so as to deposit a plating layer 130 on a modified portion 120 that has been irradiated with ultraviolet rays, and not deposit a plating layer on a portion not irradiated with ultraviolet rays. If the polycarbonate member 110 has a larger surface roughness, the plating layer is more likely to be deposited. Accordingly, by using a polycarbonate member 110 having a small surface roughness, deposition of a plating layer on the portion not irradiated with ultraviolet rays is suppressed, and it is therefore expected that selective plating on the modified portion 120 is facilitated.

There is no particular limitation on the method for applying irradiation with ultraviolet rays, but according to one embodiment, irradiation with ultraviolet rays is performed under an atmosphere containing at least one of oxygen and ozone. For example, irradiation with ultraviolet rays on the polycarbonate member 110 may be performed in the air.

To be specific, upon irradiation with ultraviolet rays, the oxygen contained in the atmosphere is decomposed to generate ozone. Furthermore, active oxygen is generated during decomposition of ozone. In addition, in the surface of the polycarbonate member 110, the bonds between molecules constituting the polycarbonate member 110 are also broken. At this time, the molecules constituting the polycarbonate member 110 react with the active oxygen, and the surface of the polycarbonate member 110 is oxidized, or in other words, hydrophilic groups such as hydroxyl groups or carboxyl groups are formed in the surface of the polycarbonate member 110. Such hydrophilic groups increase the chemical adsorption between the polycarbonate member 110 and the plating layer 130. Furthermore, in the modified portion, a catalyst ion can be selectively adsorbed when electroless plating is performed.

The energy of photons having a specific wavelength can be represented by the following equation:

E=Nhc/λ(KJ·mol ⁻¹)

N=6.022×10²³ mol⁻¹ (Avogadro's number)

h=6.626×10⁻³⁷ KJ·s (Planck constant)

c=2.988×10⁸ m·s⁻¹ (light speed)

λ=light wavelength (nm)

Here, the binding energy between oxygen molecules is 490.4 KJ·mol⁻¹. The wavelength is approximately 243 nm when converted from the binding energy based on the equation for photon energy. This indicates that the oxygen molecules in the atmosphere absorb ultraviolet rays having a wavelength of 243 nm or less and are decomposed. As a result, O₃ is generated. Furthermore, during decomposition of ozone, active oxygen is generated. At this time, under the presence of ultraviolet rays having a wavelength of 310 nm or less, ozone is efficiently decomposed and active oxygen is efficiently generated. Furthermore, ultraviolet rays having a wavelength of 254 nm most efficiently decompose ozone.

O₂ +hν(243 nm or less)→O (3P)+O (3P)

O₂+O (3P)→O₃(ozone)

O₃ +hν (310 nm or less)→O₂+O (1D) (active oxygen)

O (3P): oxygen atoms in ground state

O (1D): excited oxygen atoms (active oxygen)

On the other hand, according to another embodiment, irradiation with ultraviolet rays applied to the polycarbonate member 110 may be performed under another gas atmosphere such as an amine compound gas atmosphere such as ammonia or an amide compound gas atmosphere. In the case where the polycarbonate member 110 is modified by using ultraviolet rays by isolating the polycarbonate member 110 from the atmospheric pressure and changing the pressure or enclosing a compound gas, a wavelength suitable for the reaction can be selected as appropriate. However, it is advantageous to perform irradiation with ultraviolet rays having a maximum wavelength in a wavelength range of 243 nm or less in the air containing oxygen because modification can be performed at a low cost.

According to one embodiment, ultraviolet rays from a device that continuously emits ultraviolet rays are applied to the surface of the polycarbonate member 110. For example, ultraviolet rays from an ultraviolet lamp or an ultraviolet LED can be applied to the surface of the polycarbonate member 110. The ultraviolet rays from these devices have an intensity lower than that of an ultraviolet laser, and thus it is possible to prevent the surface of the polycarbonate member 110 from being excessively roughened.

Examples of the ultraviolet lamp include a low pressure mercury lamp and an excimer lamp. The low pressure mercury lamp can emit ultraviolet rays having wavelengths of 185 nm and 254 nm. For reference, examples of excimer lamps that can be used in the air are given below. As the excimer lamp, an Xe₂ excimer lamp is commonly used.

Xe₂ excimer lamp with a wavelength of 172 nm

KrBr excimer lamp with a wavelength of 206 nm

KrCl excimer lamp with a wavelength of 222 nm

The conditions for irradiation with ultraviolet rays are selected such that the plating layer 130 is deposited on the modified portion 120 in the plating step (S220), which will be described below. There is no particular limitation on the energy density at a primary wavelength of ultraviolet rays applied, as long as modification can proceed and the surface roughness Ra can have a desired value. The energy density at a primary wavelength of ultraviolet rays applied is, according to one embodiment, 0.1 mW/cm² or more, according to another embodiment, 0.3 mW/cm² or more, and according to still another embodiment, 1.0 mW/cm² or more. On the other hand, the energy density is, according to one embodiment, 5.0 mW/cm² or less, and according to another embodiment, 3.0 mW/cm² or less. The irradiation with ultraviolet rays having such an energy allows the polycarbonate member 110 to be modified such that the plating layer 130 is deposited thereon while increase in the surface roughness Ra is suppressed. Hereinafter, unless otherwise stated, the irradiation amount and irradiation intensity of ultraviolet rays refer to values obtained at a primary wavelength. In this specification, the primary wavelength refers to a wavelength having the highest intensity in a range of 243 nm or less. To be specific, in the case of a low pressure mercury lamp, the primary wavelength is 185 nm.

Also, ultraviolet rays from, in particular, an ultraviolet lamp, an ultraviolet LED or the like have a relatively low intensity, and thus it is thought that roughening of the polycarbonate member 110 is suppressed even if irradiation with ultraviolet rays is performed for a long period of time. From this point of view, in order to cause the modification to proceed sufficiently even when a polycarbonate member 110 having a relatively smooth surface is used, according to one embodiment, a sufficient amount of ultraviolet rays are applied. For example, the irradiation time during which ultraviolet rays are applied is, according to one embodiment, 5 minutes or more, and according to another embodiment, 10 minutes or more. There is no particular limitation on the upper limit, but the irradiation time is, according to one embodiment, 60 minutes or less, and according to another embodiment, 30 minutes or less. The cumulative irradiation amount at a primary wavelength is, according to one embodiment, 700 mJ/cm² or more, and according to another embodiment, 1000 mJ/cm² or more. Also, according to one embodiment, from the viewpoint of reducing the treatment time, ultraviolet rays are applied such that the cumulative irradiation amount is 10000 mJ/cm² or less.

At the time when the polycarbonate member 110 is irradiated with ultraviolet rays, irradiation with ultraviolet rays is controlled such that the irradiation amount reaches a desired value. The irradiation amount can be controlled by changing the irradiation time. The irradiation amount can also be controlled by changing the output of the ultraviolet lamp, the number of ultraviolet lamps, irradiation distance or the like.

As described above, hydrophilic groups are formed in the surface of the polycarbonate member 110 by irradiation with ultraviolet rays. To be specific, when irradiation with ultraviolet rays is performed under an atmosphere containing at least one of oxygen and ozone, carbonyl groups, carboxyl groups, and hydroxyl groups are formed in the surface of the polycarbonate member 110. If the irradiation time during which ultraviolet rays are applied is increased, the existence ratio of oxygen atoms in the surface of the polycarbonate member 110 increases. Also, if the irradiation time during which ultraviolet rays are applied is increased, the ratio (C═O/C—O ratio) of the number of oxygen atoms constituting a carbon-oxygen double bond (C═O) to the number of oxygen atoms constituting a carbon-oxygen single bond (C—O) tends to increase. By controlling the irradiation amount of ultraviolet rays such that the existence ratio of C═O is larger than the existence ratio of C—O in the modified surface of the polycarbonate member 110, in the plating step (S220) described later, the plating layer 130 is more likely to be deposited on the modified portion 120.

Also, in order to cause the plating layer 130 to be more likely to be deposited on the modified portion 120 in the plating step (S220) described later, the irradiation amount of ultraviolet rays is controlled such that the existence ratio of oxygen atoms in the modified surface of the polycarbonate member 110 is, according to one embodiment, 31.5% or more, and according to another embodiment, 32.0% or more.

The existence ratio of oxygen atoms and the C═0/C—O ratio can be measured by XPS measurement. In this specification, the existence ratio of oxygen atoms refers to the existence ratio (atomic percent) of oxygen atoms with respect to all atoms in the surface of the polycarbonate member 110, calculated by XPS measurement. Note that the number of hydrogen atoms is excluded from calculation because the hydrophilicity of the surface of the polycarbonate member 110 is largely affected by the ratio of carbon atoms to oxygen atoms and hydrogen atoms cannot be detected by XPS measurement. Likewise, the existence ratio of C—O refers to the existence ratio (atomic percent) of oxygen atoms constituting a carbon-oxygen single bond with respect to all atoms in the surface of the polycarbonate member 110. Also, the existence ratio of C═O refers to the existence ratio (atomic percent) of oxygen atoms constituting a carbon-oxygen double bond with respect to all atoms in the surface of the polycarbonate member 110.

The irradiation time during which ultraviolet rays are applied can be selected as appropriate according to the intensity of ultraviolet rays or the like. For example, from the viewpoint of causing the modification to proceed sufficiently, the irradiation time during which ultraviolet rays are applied is set to, according to one embodiment, 5 minutes or more, and according to another embodiment, 10 minutes or more. From the viewpoint of improving productivity, the irradiation time is set to, according to one embodiment, 30 minutes or more, and according to another embodiment, 20 minutes or less.

However, the conditions for depositing a plating layer may vary depending on the type of plating solution, the degree of contamination of the surface of the polycarbonate member 110, the concentration, temperature and pH of the plating solution, the degradation of the plating solution over time, variations in output of the ultraviolet lamp, and the like. In this case, the irradiation amount of ultraviolet rays may be determined as appropriate with reference to the above-described values.

In the irradiation step, ultraviolet rays can be applied to the entire surface of the polycarbonate member 110 such that the plating layer 130 is deposited on the entire surface of the polycarbonate member 110 in the plating step (S220). On the other hand, ultraviolet rays may be applied to a portion of the polycarbonate member 110 such that the plating layer 130 is deposited on the portion of the polycarbonate member 110 in the plating step (S220). In this case, in the irradiation step, the polycarbonate member is irradiated with ultraviolet rays such that the first region of the polycarbonate member is selectively irradiated with ultraviolet rays but the second region of the polycarbonate member is not irradiated with ultraviolet rays. By performing irradiation with ultraviolet rays in this way, in the plating step (S220), a plating layer can be formed on the first region without forming a plating layer on the second region. In this case, the modified portion 120 where the plating layer 130 is deposited in the plating step (S220) described later is formed in the first region. Here, according to one embodiment, the first region and the second region are located adjacent to each other. Also, according to another embodiment, one surface of the polycarbonate member 110 is constituted by the first region and the second region.

For example, the first region can be selectively irradiated with ultraviolet rays by irradiating the polycarbonate member 110 with ultraviolet rays via a mask having an ultraviolet ray transmitting portion corresponding to the shape of the first region. There is no particular limitation on the type of mask, and it is possible to use a metal mask having an opening corresponding to the shape of the first region, and it is also possible to use a quartz chromium mask that has an opening corresponding to the shape of the first region and in which a chromium layer is provided on a quartz substrate.

In the case where the polycarbonate member 110 has a three-dimensional shape, for example, a thin metal plate having an ultraviolet ray transmitting portion corresponding to the shape of the first region can be used as the mask. In this case, by folding the metal plate so as to fit to the polycarbonate member 110, the first region can be selectively irradiated with ultraviolet rays via the metal plate. Alternatively, by scanning the first region with ultraviolet beams, the first region can also be selectively irradiated with ultraviolet rays.

Also, according to another embodiment, it is also possible to perform irradiation with ultraviolet rays at least twice using different methods. For example, according to one embodiment, it is possible to selectively irradiate the first region with ultraviolet rays from an ultraviolet laser such that the second region is not irradiated with the ultraviolet rays, and thereafter, irradiate both the first region and the second region with ultraviolet rays from an ultraviolet lamp. The ultraviolet rays from the ultraviolet lamp may be applied to the entire surface of the polycarbonate member 110. In this case, the modified state can be controlled such that in the plating step (S220) described later, the plating layer 130 is deposited on the first region that has been modified by using both the ultraviolet laser and the ultraviolet lamp. On the other hand, the modified state can be controlled by adjusting the irradiation amount of ultraviolet rays from the ultraviolet lamp such that the plating layer 130 is not deposited on the insufficiently modified second region that has been modified by using only the ultraviolet lamp.

This method is advantageous in that because selective irradiation is performed by using the laser with high linearity, the shape of the resulting plating layer 130 can be controlled precisely. In the case of using the laser, the temperature of the polycarbonate member 110 is less likely to increase as compared to the case of using the lamp. For this reason, in the case of selectively irradiating the first region with ultraviolet rays via a photomask, an offset of the position where ultraviolet rays are applied caused by a difference in thermal expansion coefficient between the photomask and the polycarbonate member 110 can be suppressed. On the other hand, by using ultraviolet rays from the ultraviolet lamp that can generate active oxygen the more, the first region can be sufficiently modified such that the plating layer 130 well adheres to the polycarbonate member 110.

In the present embodiment, a strong acid treatment or a strong alkali treatment is not performed between the modification step (S210) and the plating step (S220). Generally, for the purpose of increasing the surface roughness of a resin article such as the polycarbonate member 110, a strong acid treatment or a strong alkali treatment is performed on the resin article. By increasing the surface roughness of a resin article, the adhesion between the resin article and the plating layer is improved by an anchoring effect. However, it was found that, in the case where the polycarbonate member 110 is modified by ultraviolet rays as in the present embodiment, if a strong acid treatment or a strong alkali treatment is performed, the plating layer 130 is unlikely to be deposited.

Although the reason is not clearly known, the present inventors assume the reason to be that the modified portion 120 created by irradiation with ultraviolet rays is affected and removed by a strong acid treatment or a strong alkali treatment. In particular, in the case of using a smooth polycarbonate member 110, a rough surface created in the modified portion 120 as a result of irradiation with ultraviolet rays is considered to be a very fine rough surface. It is assumed that such a fine rough surface is easily removed by a strong acid treatment or a strong alkali treatment.

In the present embodiment, neither a strong acid treatment nor a strong alkali treatment is performed. Accordingly, the plating layer 130 can be sufficiently deposited on the modified portion 120. Also, by not performing a strong acid treatment or a strong alkali treatment, a resin article 100 having a plating layer can be manufactured in a less number of steps.

In this specification, the strong acid treatment refers to an acid treatment that uses a treatment solution having a pH of 1 or less. Likewise, the strong alkali treatment used in this specification refers to an alkali treatment that uses a treatment solution having a pH of 13 or more.

Also according to one embodiment, in order to maintain the smoothness, an additional modification treatment is not performed on at least a part of the modified portion 120 between the modification step (S210) and the plating step (S220). As a specific example, an additional modification treatment is not performed between irradiation with ultraviolet rays in the modification step (S210) and a conditioner treatment or a catalyst application treatment in the plating step (S220). As another specific example, an additional modification treatment is not performed between irradiation with ultraviolet rays in the modification step (S210) and immersion of the polycarbonate member 110 into an electroless plating solution in the plating step (S220). Examples of the additional modification treatment include a photoexcited ashing treatment, a plasma ashing treatment, an oxidation treatment that uses a chemical, and laser irradiation.

A part or all of the surface of the polycarbonate member 110 before the plating layer 130 is formed in the plating step (S220) has a surface roughness of, according to one embodiment, 100 nm or less, according to another embodiment, 10 nm or less, and according to still another embodiment, 2 nm or less. Also, a part or all of the surface of the polycarbonate member 110 before the plating layer 130 is formed in the plating step (S220) has a maximum height roughness Rz of, according to one embodiment, 100 nm or less, according to another embodiment, 30 nm or less, and according to still another embodiment, 10 nm or less.

In particular, as a result of the modified portion 120 of the polycarbonate member 110 having a smaller surface roughness, as will be described later, the high frequency propagation characteristics of the resulting plating layer 130 are improved, and the light reflectance of the plating layer 130 is improved. Also, as a result of a portion other than the modified portion 120 in the polycarbonate member 110 having a smaller surface roughness, as will be described later, the light transmission of the portion in the polycarbonate member 110 is improved. Furthermore, as a result of a portion other than the modified portion 120 in the polycarbonate member 110 having a smaller surface roughness, the plating layer 130 is unlikely to be deposited on the portion, and it is therefore expected that selective plating on the modified portion 120 is facilitated.

Plating Step

In the plating step (S220), the plating layer 130 is formed, by electroless plating, on the surface of the polycarbonate member 110 that has been modified in the modification step (S210). To be specific, the plating layer 130 is formed on the surface of the modified portion 120 formed in the modification step (S210). The resin article 100 having a plating layer is manufactured in this way.

There is no particular limitation on the specific method of electroless plating. Examples of electroless plating that can be used in the present invention include electroless plating that uses a formalin-based electroless plating bath, and electroless plating that uses, as a reducing agent, hypophosphorous acid, which is easier to use than formalin although the deposition speed is low. Also, in order to form a thick plating layer, the plating layer 130 may be formed by a high-speed electroless plating method. Other specific examples of electroless plating include electroless nickel plating, electroless copper plating, and electroless copper nickel plating.

The plating layer 130 may be formed by electroless plating alone. However, the plating layer 130 formed by electroless plating is often thin. Accordingly, in order to reduce the resistance of the plating layer 130, additional electroplating may be performed on the polycarbonate member 110 after electroless plating. As a result of the electroplating, an additional electroplating layer is deposited on the electroless plating layer obtained by electroless plating. In other words, the plating layer 130 may have a stack structure composed of a plurality of metal layers. According to the electroplating method, it is possible to easily deposit a thicker plating layer than that formed by the electroless plating method. In this case, the electroplating layer alone, or both the electroless plating layer and the electroplating layer together, function as the plating layer 130.

Examples of the material of the metal layer formed by electroplating include, but are not limited to, copper, nickel, copper-nickel alloy, zinc oxide, zinc, silver, cadmium, iron, cobalt, chromium, nickel-chromium alloy, tin, tin-lead alloy, tin-silver alloy, tin-bismuth alloy, tin-copper alloy, gold, platinum, rhodium, palladium, and palladium-nickel alloy. Also, silver or the like may be deposited on the plating layer 130 by displacement plating.

According to one embodiment, the electroless plating can be performed by using an activator-accelerator method as described below.

1. Conditioner Treatment

The polycarbonate member 110 is immersed in a solution containing a binder material for binding the polycarbonate member 110 and a catalyst ion. With this treatment, it is thought that the binder material is applied to the modified portion 120. An example of the binder material is a cation polymer or the like.

2. Activator Treatment

The polycarbonate member 110 is immersed in a solution containing a catalyst ion. With this treatment, it is thought that the catalyst ion is applied to the modified portion 120 via the binder material. An example of the catalyst ion is a palladium complex such as a hydrochloric acid palladium complex, or the like.

3. Accelerator Treatment

The polycarbonate member 110 is immersed in a solution containing a reducing agent so as to reduce and deposit a catalyst ion. With this treatment, it is thought that the catalyst is deposited on the modified portion 120. Examples of the reducing agent include hydrogen gas, dimethylamine borane and sodium borohydride.

4. Electroless Plating Treatment

The polycarbonate member 110 is immersed in an electroless plating solution so as to deposit the plating layer 130 on the deposited catalyst. With this treatment, the plating layer 130 is formed on the modified portion 120.

The electroless plating according to the method as described above can be performed by using, for example, an electroless plating solution set such as a plating solution set AISL available from JCU Corporation. However, as described above, an alkali treatment that uses an alkali treatment solution included in the plating solution set is not performed in the present embodiment.

According to another embodiment, as the catalyst ion, a palladium complex that easily adheres to the modified portion 120 and has a positive charge in at least a part thereof is used. In order to improve the adhesion of the catalyst ion to the modified portion 120, according to one embodiment, a solution containing a palladium complex ion having a positive charge in the solution is used. An example of the palladium complex having a positive charge in at least a part thereof is a complex containing an amine-based coordinating ligand. Also, another example of the palladium complex having a positive charge in at least a part thereof is a palladium-basic amino acid complex. In this case, it is not necessary to immerse the polycarbonate member 110 in a solution containing a binder material so as to increase the affinity between the polycarbonate member 110 and the catalyst ion.

According to another embodiment, it is possible to apply a colloid catalyst such as a tin-palladium colloid catalyst to the modified portion of the polycarbonate member 110. On the other hand, from the viewpoint of depositing the plating layer 130 more selectively on the modified portion 120, an activator-accelerator method is used as the method for applying an electroless plating catalyst. The activator treatment and the accelerator treatment may be collectively referred to as a catalyst application treatment.

According to one embodiment, neither a strong acid treatment nor a strong alkali treatment is performed in the plating step. For example, according to one embodiment, a conditioner treatment, an activator treatment, an accelerator treatment, and an electroless plating treatment are performed under mild conditions. With this configuration, it is possible to suppress a reduction in the adhesion of the plating layer 130 caused by the modified portion 120 being removed before the plating layer 130 is deposited. Also, with this configuration, it is possible to suppress an increase in the surface roughness of a portion where the plating layer 130 is not provided in the polycarbonate member 110.

There is no particular limitation on the material of the plating layer 130 formed in the plating step, and any metal material can be used. For example, in the case where the resin article 100 having a plating layer is used as a wiring board, an electroconductive material is used as the material of the plating layer 130. Also, in the case where the resin article 100 having a plating layer is used in an encoder, or more specifically, in a code wheel of a rotary encoder, a material having a desired optical property is used as the material of the plating layer 130. Specific examples of the material of the plating layer 130 include, but are not limited to, copper, nickel, and copper-nickel alloy.

The plating layer 130 can have any shape. According to one embodiment, the plating layer 130 is disposed in a predetermined pattern on the polycarbonate member 110. The predetermined pattern may be, but is not necessarily limited to, a mesh pattern, a stripe pattern, a square pattern, a rectangular pattern, a rhombic pattern, a honeycomb pattern, a curved pattern, and an amorphous pattern. For example, in the case where the resin article 100 having a plating layer is used as a wiring board, the plating layer 130 may have an elongated conductive wire pattern.

The thickness of the plating layer 130 is, according to one embodiment, 0.02 μm or more, and according to another embodiment, 5.0 μm or more, but there is no particular limitation thereon. Also, according to one embodiment, the thickness is 100 μm or less, and according to another embodiment, 20 μm or less. As a result of the plating layer 130 being thin, the line width in the pattern can be easily reduced, and by increasing the thickness of the plating layer 130, for example, a sufficiently low resistance can be achieved. As used herein, the thickness of the plating layer 130 refers to the thickness of the plating layer 130 in a direction vertical to the surface of the polycarbonate member 110.

According to one embodiment in which a portion of the surface of the polycarbonate member 110 is selectively irradiated with ultraviolet rays in the modification step (S210), the plating layer 130 is deposited on the modified portion 120 that has been irradiated with ultraviolet rays. On the other hand, the plating layer 130 is not deposited on the portion that has not been irradiated with ultraviolet rays. For this reason, the plating layer 130 having a desired pattern can be formed on the polycarbonate member 110. According to this embodiment, it is not necessary to perform patterning on the plating layer 130 by a method such as etching after formation of the plating layer 130 in order to obtain a plating layer having a desired pattern. An etching treatment easily causes damage to the polycarbonate member 110, and thus this embodiment is advantageous in that the resin article 100 having a smooth plating layer is obtained.

In the manner described above, the resin article 100 having a plating layer in which the plating layer is formed on the polycarbonate member is obtained. The surface roughness of the polycarbonate member 110 at an interface between the polycarbonate member 110 and the plating layer 130 is, according to one embodiment, 100 nm or less, according to another embodiment, 10 nm or less, and according to still another embodiment, 2 nm or less. Also, the maximum height roughness Rz of the polycarbonate member 110 at the interface between the polycarbonate member 110 and the plating layer 130 is, according to one embodiment, 100 nm or less, according to another embodiment, 30 nm or less, and according to still another embodiment, 10 nm or less.

A smaller surface roughness of the polycarbonate member 110 at the interface between the polycarbonate member 110 and the plating layer 130 indicates that the surface of the plating layer 130 is smoother. When the plating layer 130 as described above is used as a wire, because the loss of high frequency signal is low, the resin article 100 having the plating layer 130 as described above can be used as a wiring board having good high frequency propagation characteristics.

For example, a surface of the plating layer 130 that is opposite to the polycarbonate member 110 has a surface roughness of, according to one embodiment, 100 nm or less, according to another embodiment, 10 nm or less, and according to still another embodiment, 2 nm or less. Also, the surface of the plating layer 130 opposite to the polycarbonate member 110 has a maximum height roughness Rz of, according to one embodiment, 100 nm or less, according to another embodiment, 30 nm or less, and according to still another embodiment, 10 nm or less. It is thought that the surface roughness of the surface of the plating layer 130 opposite to the polycarbonate member 110 reflects the surface roughness of the modified portion 120 before the plating layer 130 is formed.

Also, the smaller the surface roughness of the polycarbonate member 110 at the interface between the polycarbonate member 110 and the plating layer 130 is, the higher the light reflectance of the plating layer 130 via the polycarbonate member 110 tends to be. Accordingly, the plating layer 130 as described above can be used as a mirror surface member. For example, the resin article 100 having the plating layer 130 as described above can be used as a component of an encoder such as a code wheel of a rotary encoder. For example, the resin article 100 having a plating layer may be a code wheel having a light transmitting portion and a light reflection portion.

For example, the light reflectance of the plating layer 130 via the polycarbonate member 110 at a wavelength of 650 nm is, according to one embodiment, 30% or more, according to another embodiment, 50% or more, and according to still another embodiment, 65% or more. Also, the light reflectance of the plating layer 130 via the polycarbonate member 110 at a wavelength of 800 nm is, according to one embodiment, 30% or more, according to another embodiment, 50% or more, and according to still another embodiment, 70% or more. In particular, because the reflectance of the plating layer 130 with respect to near-infrared light is high, the resin article 100 having a plating layer is advantageously used as a component of an encoder that uses near-infrared light rays.

Also, in a part or all of a portion where the plating layer 130 is not provided in the polycarbonate member 110, the polycarbonate member 110 has a surface roughness of, according to one embodiment, 100 nm or less, according to another embodiment, 10 nm or less, and according to still another embodiment, 2 nm or less. Also, in a part or all of a portion where the plating layer 130 is not provided in the polycarbonate member 110, the polycarbonate member 110 has a maximum height roughness Rz of, according to one embodiment, 100 nm or less, according to another embodiment, 30 nm or less, and according to still another embodiment, 10 nm or less.

A smaller surface roughness of the polycarbonate member 110 indicates that the light transmission of the polycarbonate member 110 is improved because light is unlikely to scatter on the surface of the polycarbonate member 110. In other words, the resin article 100 having a plating layer that includes the polycarbonate member 110 as described above has higher transparency. For example, the resin article 100 having the plating layer 130 as described above can be used as a component of an encoder such as a code wheel of a rotary encoder.

According to the manufacturing method according to the present embodiment, even when the polycarbonate member 110 has a small surface roughness, it is possible to provide the plating layer 130 on the polycarbonate member 110 without significantly roughening the polycarbonate member 110.

EXAMPLES Example 1

First, a transparent polycarbonate member 110 (trade name: Eupilon Sheet available from Mitsubishi Gas Chemical Company, Inc., with a thickness of 300 μm) was irradiated with ultraviolet rays. To be specific, ultraviolet rays were applied via a quartz chromium mask such that, in the polycarbonate member 110, a region 310 shown in FIG. 3 was irradiated with ultraviolet rays, whereas a region 320 located adjacent to the region 310 was not irradiated with ultraviolet rays. The ultraviolet rays were applied for 15 minutes by using a low pressure mercury lamp (UV300 available from Samco, Inc., with a primary wavelength of 185 nm). The irradiation amount of ultraviolet rays was 1215 mJ/cm². Also, the energy density at a primary wavelength of ultraviolet rays applied to the surface of the polycarbonate member 110 was 1.35 mW/cm². The surface roughness of the polycarbonate member 110 before irradiation with ultraviolet rays was 0.49 nm.

XPS measurement was performed on the surface of the polycarbonate member 110 irradiated with ultraviolet rays, and it was found that the existence ratio of oxygen atoms was 32.46%, the C—O ratio was 15.76%, and the C═O ratio was 16.70%. As the XPS analysis apparatus, Theta Probe available from Thermo Fisher Scientific, Inc. was used. As the excitation X rays, monochromatic X rays (Al Kα 1486.6 eV) from an Al target were used. For measurement for the purpose of neutralizing a charge, irradiation with electron beams and argon ions was performed. The measurement conditions for composition analysis were as follows: an X ray beam diameter of 300 μm, a step energy of 0.1 eV, and a pass energy of 100 eV.

Next, a conditioner treatment was performed on the polycarbonate member 110. Note that neither a strong acid treatment nor a strong alkali treatment was performed between irradiation with ultraviolet rays and the conditioner treatment. To be specific, a conditioner solution included in a plating solution set AISL available from JCU Corporation was heated to 50° C., and the polycarbonate member 110 was immersed in the plating solution for 2 minutes. After that, the polycarbonate member 110 was washed with water heated to 50° C. and thereafter washed with water.

Next an activator treatment (catalyst ion application treatment) was performed on the polycarbonate member 110 that had undergone the conditioner treatment. To be specific, an activator solution included in the plating solution set AISL available from JCU Corporation was heated to 50° C., and the polycarbonate member 110 was immersed in the activator solution for 2 minutes. After that, the polycarbonate member 110 was washed with water.

Next, an accelerator treatment (reduction treatment) was performed on the polycarbonate member 110 that had undergone the activator treatment. To be specific, an accelerator solution included in the plating solution set AISL available from JCU Corporation was heated to 40° C., and the polycarbonate member 110 was immersed in the accelerator solution for 2 minutes. After that, the polycarbonate member 110 was washed with water. The polycarbonate member 110 in the region 310 irradiated with ultraviolet rays had a surface roughness of 0.40 nm and a maximum height roughness Rz of 4.83 nm.

Next, electroless copper nickel plating was performed on the polycarbonate member 110 that had undergone the accelerator treatment. To be specific, an electroless copper nickel plating solution included in the copper nickel plating solution set AISL available from JCU Corporation was heated to 60° C., and the polycarbonate member 110 was immersed in the electroless copper nickel plating solution for 5 minutes. After that, the polycarbonate member 110 was washed with water. In this way, a resin article 100 having a plating layer was produced.

Through the treatments as described above, a copper nickel plating layer serving as the plating layer 130 was formed in the region 310 irradiated with ultraviolet rays in the polycarbonate member 110. On the other hand, the plating layer 130 was not formed in the region 320 that was not irradiated with ultraviolet rays.

The light reflectance of the resulting plating layer 130 was measured via the polycarbonate member 110. The result of measurement is shown in FIG. 4. To be specific, the reflectance at a wavelength of 600 nm was 59.0%, the reflectance at a wavelength of 700 nm was 69.3%, the reflectance at a wavelength of 800 nm was 73.9%, the reflectance at a wavelength of 900 nm was 77.5%, and the reflectance at a wavelength of 1000 nm was 79.5%.

Example 2

A resin article 100 having a plating layer was produced in the same manner as in Example 1 except that the irradiation time during which ultraviolet rays were applied was set to 0, 1, 3 or 5 minutes. Also, XPS measurement was performed on the surface of the polycarbonate member 110 that had been irradiated with ultraviolet rays in the same manner as in Example 1.

The result of the XPS measurement is as follows.

Existence Irradiation ratio of C—O C═O time oxygen atoms ratio ratio 0 minutes 13.84%  9.04%  4.80% 1 minute 22.45% 14.54%  7.91% 3 minutes 30.77% 16.67% 14.10% 5 minutes 31.02% 16.19% 14.83%

When the irradiation time during which ultraviolet rays were applied was set to 0 minutes or 1 minute, the plating layer 130 was not successfully formed. When the irradiation time during which ultraviolet rays were applied was set to 3 minutes or 5 minutes, the plating layer 130 was formed only in a portion of the region 310 irradiated with ultraviolet rays.

Example 3

A resin article 100 having a plating layer was produced in the same manner as in Example 1 except that nickel plating was performed instead of copper nickel plating. A nickel plating layer serving as the plating layer 130 was formed in the region 310 irradiated with ultraviolet rays on the surface of the polycarbonate member 110. On the other hand, the plating layer 130 was not formed in the region 320 that was not irradiated with ultraviolet rays.

Example 4

A resin article 100 having a plating layer was produced in the same manner as in Example 1 except that copper plating was performed instead of copper nickel plating. A copper plating layer serving as the plating layer 130 was formed in the region 310 irradiated with ultraviolet rays on the surface of the polycarbonate member 110. On the other hand, the plating layer 130 was not formed in the region 320 that was not irradiated with ultraviolet rays.

Comparative Example 1

An attempt was made to produce a resin article 100 having a plating layer in the same manner as in Example 1 except that the entire surface of the polycarbonate member 110 was irradiated with ultraviolet rays and an alkali treatment was added between the irradiation with ultraviolet rays and the conditioner treatment. In the alkali treatment, an alkali treatment solution included in a plating solution set AISL available from JCU Corporation was heated to 50° C., and the polycarbonate member 110 was immersed in the alkali treatment solution for 2 minutes, and thereafter the polycarbonate member 110 was washed with water. The alkali treatment solution was an aqueous solution containing 3.7 wt % sodium hydroxide.

Although a plurality of attempts were made, the result was either that the plating layer 130 was not formed on the polycarbonate member 110, or that the plating layer 130 was formed in the form of sparsely distributed dots. Accordingly, a uniform plating layer 130 was not obtained. The polycarbonate member 110 that had undergone the alkali treatment had a surface roughness of 0.28 nm.

Comparative Example 2

An attempt was made to produce a resin article 100 having a plating layer in the same manner as in Example 1 except that the entire surface of the polycarbonate member 110 was irradiated with ultraviolet rays and an acid treatment was added between the irradiation with ultraviolet rays and the conditioner treatment. In the acid treatment, an acid treatment solution was used, and the polycarbonate member 110 was immersed in the solution at 70° C. for 1 minute, and thereafter, the polycarbonate member 110 was washed with water. As the acid treatment solution, an aqueous solution containing 40% sulfuric acid was used.

The plating layer 130 was formed on the polycarbonate member 110 that had been irradiated with ultraviolet rays, but the plating layer 130 was not uniform, and the polycarbonate member was exposed at some regions.

The polycarbonate member 110 that had undergone the accelerator treatment had a surface roughness of 0.48 nm and a maximum height roughness Rz of 13.7 nm.

Also, the light reflectance of the resulting plating layer 130 as measured via the polycarbonate member 110. The result of measurement is shown in FIG. 4. To be specific, the reflectance at a wavelength of 600 nm was 50.9%, the reflectance at a wavelength of 700 nm was 63.1%, the reflectance at a wavelength of 800 nm was 69.5%, the reflectance at a wavelength of 900 nm was 74.4%, and the reflectance at a wavelength of 1000 nm was 77.4%. It can be seen from a comparison with the result of Example 1 that the light reflectance decreases as the surface roughness of the polycarbonate member 110 at the interface between the polycarbonate member 110 and the plating layer 130 is increased.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2014-263303, filed Dec. 25, 2014, which is hereby incorporated by reference herein in its entirety. 

What is claimed is:
 1. A method of manufacturing a resin article having a plating layer, comprising: modifying a surface of a polycarbonate member by irradiating the surface with ultraviolet rays; and forming a plating layer on the modified surface by electroless plating, wherein neither a strong acid treatment nor a strong alkali treatment is performed between the modification and the forming.
 2. The method of manufacturing a resin article having a plating layer according to claim 1, wherein neither the strong acid treatment nor the strong alkali treatment is performed in the forming.
 3. The method of manufacturing a resin article having a plating layer according to claim 1, wherein the strong acid treatment is an acid treatment that uses a treatment solution having a pH of 1 or less, and the strong alkali treatment is an alkali treatment that uses a treatment solution having a pH of 13 or more.
 4. A method of manufacturing a resin article having a plating layer, comprising: modifying a surface of a polycarbonate member by irradiating the surface with ultraviolet rays; and forming a plating layer on the modified surface by electroless plating, wherein an energy density at a primary wavelength of the ultraviolet rays applied to the surface in the modification is 5.0 mW/cm² or less, and an irradiation time is 5 minutes or more.
 5. A method of manufacturing a resin article having a plating layer, comprising: modifying a surface of a polycarbonate member by irradiating the surface with ultraviolet rays; and forming a plating layer on the modified surface by electroless plating, wherein the modification is performed such that in the modified surface, an existence ratio of carbon-oxygen double bonds is larger than an existence ratio of carbon-oxygen single bonds.
 6. The method of manufacturing a resin article having a plating layer according to claim 1, wherein the surface of the polycarbonate member includes a first region and a second region, the modification includes irradiating the first region with ultraviolet rays such that the second region is not irradiated with ultraviolet rays, and in the forming, the plating layer is formed on the first region such that the plating layer is not formed on the second region.
 7. The method of manufacturing a resin article having a plating layer according to claim 1, wherein in the modification, irradiation with ultraviolet rays having a primary wavelength of 243 nm or less is performed under an atmosphere containing at least one of oxygen and ozone.
 8. The method of manufacturing a resin article having a plating layer according to claim 1, wherein in the forming, the electroless plating is performed by an activator-accelerator method.
 9. The method of manufacturing a resin article having a plating layer according to claim 1, wherein the polycarbonate member before being modified in modification has a surface roughness Ra of 100 nm or less.
 10. The method of manufacturing a resin article having a plating layer according to claim 1, wherein the modified surface of the polycarbonate member has a surface roughness Ra of 100 nm or less.
 11. The method of manufacturing a resin article having a plating layer according to claim 1, wherein the polycarbonate member at an interface between the polycarbonate member and the plating layer has a surface roughness of 100 nm or less.
 12. The method of manufacturing a resin article having a plating layer according to claim 1, wherein the plating layer has a surface roughness of 100 nm or less.
 13. The method of manufacturing a resin article having a plating layer according to claim 1, wherein a portion where the plating layer is not provided in the polycarbonate member has a surface roughness of 100 nm or less.
 14. The method of manufacturing a resin article having a plating layer according to claim 1, wherein a light reflectance at a wavelength of 650 nm of the plating layer via the polycarbonate member is 65% or more. 